Process for the preparation of thiazoles

Abstract

An improved process for the preparation of thiazoles is disclosed. The process utilizes a substituted imine and sulfur dioxide heated in the presence of a catalyst. The thiazoles are known important chemical intermediates.

We claim: 
     
       1. A process for the preparation of a compound having the formula ##STR15## wherein R 1 , R 2  and R 3  are independently hydrogen, loweralkyl, phenyl or substituted phenyl wherein the substituent is one or two of loweralkyl or halogen, which comprises reacting an imine having the formula: ##STR16## wherein R 1 , R 2  and R 3  are as defined above, with sulfur dioxide in the presence of a catalyst consisting of a mixture of from 0.1 to 2% by weight of zirconium oxide, from 85 to 98% by weight of an alkaline earth metal oxide and from 1 to 15% by weight of an alkali metal hydroxide. 
     
     
       2. The process of claim 1 wherein the catalyst consists of 89% by weight of an alkaline earth metal oxide; 10% by weight of an alkali metal hydroxide, and 1% by weight of zirconium oxide. 
     
     
       3. The process of claim 2 wherein the catalyst consists of 89% by weight of calcium oxide, 10% by weight of sodium hydroxide and 1% by weight of zirconium oxide. 
     
     
       4. The process of claim 1 wherein the reaction is maintained at a temperature of from 400°-500° C. 
     
     
       5. The process of claim 4 wherein the reaction is maintained at a temperature of from 440°-480° C. 
     
     
       6. The process of claim 5 wherein the reaction is maintained at a temperature of about 460° C. 
     
     
       7. The process of claim 1 wherein from 10 moles of the imine is used for each mole of sulfur dioxide to 1 mole of the imine for 10 moles of sulfur dioxide. 
     
     
       8. The process of claim 1 wherein substantially equimolar amounts of the imine and sulfur dioxide are used. 
     
     
       9. The process of claim 1 wherein the imine and sulfur dioxide are present in the reaction stream at from 2-12 mole percent of each component. 
     
     
       10. The process of claim 9 wherein the imine and sulfur dioxide are present in the reaction stream at about 8 mole percent of each component. 
     
     
       11. The process of claim 1 wherein the product is 4-methylthiazole.